A/D converter apparatus and D/A converter apparatus including a digital filter

1. An A/D converter apparatus comprising: an anti-aliasing filter for removing a frequency component corresponding to an aliasing noise generated by sampling; an A/D converter for converting an analog signal output from the anti-aliasing filter into a digital signal; a SINC filter for removing a frequency component corresponding to an aliasing noise generated by down-sampling from a signal output from the A/D converter; a first decimator for down-sampling a signal output from the SINC filter; a low pass filter for removing a frequency component corresponding to an aliasing noise generated by down-sampling from a signal output from the first decimator; a second decimator for down-sampling a signal output from the low pass filter; a high pass filter for removing a DC component from a signal output from the second decimator; and a third decimator for down-sampling a signal output from the high pass filter.

2. A D/A converter apparatus comprising: a first interpolator for up-sampling a digital input signal; a high pass filter for removing a DC component from an output of the first interpolator; a second interpolator for up-sampling a signal output from the high pass filter; a first low pass filter for removing an out-of-band noise from a signal output from the second interpolator; a third interpolator for up-sampling a signal output from the first low pass filter; a second low pass filter for removing an out-of-band noise from a signal output from the third interpolator; a D/A converter for converting a digital signal output from the second low pass filter into an analog signal; and a smoothing filter for smoothing the analog signal output from the d/a converter.

3. An A/D and D/A converter apparatus having the A/D converter apparatus according to claim 1 and the D/A converter apparatus according to claim 2 , comprising a sharing means for sharing the high pass filter and the low pass filter in the A/D converter apparatus and the high pass filter and the low pass filter in the D/A converter apparatus.

4. The A/D and D/A converter apparatus according to claim 3 , wherein the sharing means comprises: a first switch for selecting the output of the second decimator or the output of the first interpolator to supply it to the high pass filter; a second switch for supplying the output of the high pass filter to the third decimator or the second interpolator; and a third switch for selecting the output of the first decimator or the output of the second interpolator to supply it to the low pass filter.